Hydrometallurgical process using resin-neutralized-solution of a heap leaching effluent

ABSTRACT

The present invention refers to a hydro-metallurgical process using resin-in-neutralized-solution in heap leaching effluent. More specifically, the process is applicable to lateritic ore, nickel oxidate, cobalt oxidate or a mixture containing metals of interest—nickel, cobalt and other secondary metals, wherein ore is leached by adding an acid or a base with possible pH adjustment, aided by acid or base with neutralization of heap leaching effluent, by adding lime, limestone, soda or ammonia in the temperature of 70° to 95° C. range, at pH in the pH4 to pH5 range; wherein soluble impurity species can be reduced or cementing/complexation techniques, comprising a neutralized leaching effluent, as slurry, made up of solid particles (precipitated compounds) and solution, but ore-free; which is fed into the RINS (resin-in-neutralized-solution) circuit, with no need for solid-liquid separation; wherein the resin-in-neutralized-solution circuit comprises multiple sequential vats stirred in countercurrent flow and wherein the loaded resin is separated from the slurry by screening.

RELATED APPLICATION

This application claims priority from U.S. provisional application Ser. No. 60/968,599 which was filed on Aug. 29, 2007.

TECHNICAL FIELD

The present invention is related to the field of the use of resin-in-neutralized-solution in the process of heap leaching effluent.

BACKGROUND OF THE INVENTION

One of the difficulties facing nickel lateritic ore processing plants occurs in assorted conventional hydrometallurgical flowchart choices that considerably differ among themselves. There is no standard optimized flowchart meeting these ores' chemical and mineral needs. Various flowcharts show technical-economic restrictions and constraints that must be minimized or even downright eliminated by optimizing unit operations involved. An ever-growing complexity (chemical, mineral, size) of ore deposits is another major hurdle. Many companies ideally aspire to find a large high-grade deposit, easy to mine and to process. Conventional technologies can be used with low technical risk, anchored on recent hydrometallurgical operations as Cawse, Murrin Murrin, Bulong and others.

There is a perception that embracing new technologies is a huge risk. No wonder that conventional technologies are often chosen. However, oftentimes excessive trust in conventional technologies triggers a series of even more serious problems—for instance, inadequate or nonexistent pilot operation, lack of qualified personnel, engineering faults in design and in cost projection, oversimplifying operations to save cost and time, over demanding schedules, inadequate or poor resources and inputs, market under-assessment, and other shortcomings. On the other hand, new technologies pay off and are worthwhile but often demand a long R&D horizon before reaching excellence. Some of their hurdles are: late start-up problems due to operational troubles often caused by engineering design flaws; late ramp-up and consequent closing of plant; operating problems and overall complexity; low operating efficiency, etc.

A major challenge faced by some plants is that the solid-liquid separation stage creates major problems for conventional circuits. Due to poor pulp settlement in a counter-current decantation (“CCD”) stage, roughly 10% of soluble nickel and cobalt are lost in rejects and in waste. In order to minimize such significant loss, a series of at least six large thickeners (over 50 m diameter in each stage) are used in solid-liquid separation so as to ensure correct solid settlement and to produce clean overflow. Thus, capital cost in a simple CCD stage, with conventional thickeners, can reach 30% of a titanium autoclave used in a high pressure acid leaching process (“HPAL”). Even more expensive thickeners are needed if chlorides are present, as in some lateritic deposits in arid regions. In addition to capital cost, operating costs are also high including not just power consumption for each rake but also flocculants which are needed to settle fines. Flocculant consumption ranges from 200 to 800 grams per ton of solids and this increases a plant's total operating cost by as much as 10%.

Another obstacle to be overcome is recovering nickel and cobalt from the resulting pressure leach solution (“PLS”) due to impurities and low concentration of value metals of interest. Ionic exchange is an efficient method to overcome these barriers. It is effective in low concentrations and selectivity can be much enhanced if the correct ionic exchange resin is used.

Several factors encourage not just optimization of pre-existing flowcharts but also propose new highly innovative process techniques. A highly representative factor is the high price of nickel, driven by slow growth of primary nickel production and increased Asian nickel consumption, suggesting a hectic race to develop new proposals of hydrometallurgical processes. Many projects so far could not be economically feasible because they were anchored on older long-term forecasting of nickel prices.

Heap leaching has been used in Brazil, the USA, Australia, Chile and elsewhere as an efficient ore-treatment method, especially on ores from small deposits or low-grade ores. In this process, coarse ore is heaped on a previously waterproofed surface and prepared to remain slightly tilted, thus ensuring drainage of the resulting slurry. Leaching slurry is sprinkled or dripped on top of the stockpile, percolating down to its bed and progressively dissolving some rock parts until reaching the waterproofed stockpile bottom. Leaching liquor is then led to the recovery stage.

Performance of an ore about to undergo stockpile leaching can be evaluated through column and small heap tests. These tests provide maximum metal extraction in leach consumption and their concentration in the leaching slurry and also ensure its time evolution and leaching slurry concentration. However, scaling is difficult because it is hard to reproduce geometric proportions of industrial stockpiles and their hydrodynamic conditions. Associated with costs and the time of assays, they call for use of phenomenological models aimed at circuit analysis and the project.

In addition to the existence of major local ore deposits, choosing heap leaching as the ore-extraction technique is influenced by factors such as terrain topography (avoiding mountainous areas) and local hydrology. Maintaining a certain acid concentration is necessary to render the process effective and economic. However, this concentration can be affected by regional hydrological conditions. Where the climate is arid and evaporation rates high much additional water may be required to maintain the necessary water volume in the leaching circuit. Under humid weather conditions, on the other hand, infiltrated rainfall water can add water to the circuit decreasing solution concentration and jeopardizing the whole industrial process.

Material to be processed can come from various sources, such as newly mined ore, previously piled ore, waste residues from conventional processing, etc. Most applications involving heap leaching use newly mined ore which is more economically feasible for processing large volumes of low-metal-grade ores.

The paramount objective in ore preparation is to produce fragments sufficiently small to allow solution-metal contact while ensuring adequate permeability for flow through the entire heap. In some cases, ore pre-treatment (such as direct leaching of run-of-mine ore extracted from mine in blocks up to 120 cm diameter) can be dispensed with.

In other cases, crushing and/or agglomeration may be required. The permeability coefficient in ores with high percentage of fines can be very low, resulting in long time intervals for treatment and in low amounts of metal produced. In such cases, agglomeration with added ligants seeks to form a dense and porous material, stable when handled, which is stacked and percolates in the leaching solution.

The leaching solution, based on sulfuric acid in nickel mining, is hauled from the barren pond to the heap through a piping system. A set of pumps is also necessary to supply sufficient pressure to the sprinklers. A basic operational requirement is that the solution be uniformly distributed on the heap top and that typical discharges ensure non-saturated flow along the heap top. The chemical reaction in which metals are dissolved demand the presence of oxygen. Therefore, non-saturated flow is essential for the leaching process. A layer of permeable material is generally placed directly on the waterproof coating prior to heap construction. The purpose of this layer is to make possible solution drainage and to protect the coating during stockpile formation.

The pregnant solution is collected from the heap through a drainage system comprising perforated pipes placed inside the permeable layer on the heap pad. These pipes help decrease the pressure load on the heap pad and are connected to a collect system, which deposits the fluid in a pregnant solution pond.

The stockpile must be designed as permeable as possible, with homogeneous-flow characteristics, in order to allow swift flow through the ore and its collection at the pad drainage system. It should also allow solution contact with as much ore as possible and oxygen maximization in the stockpile's empty spaces. One or more layers are used in heap construction. Total heap height depends on its foundation, on its pad resistance, on its coating, on terrain topography, on ore mechanical properties, and on the type of equipment used in heap construction. Alternatives to heap construction include hauling material in conveyor belts, unloading it by truck and spreading it out by motor scraper, etc. Equipment traffic can fragment and compact ore, thus creating low surface permeability. At the end of heap construction, this zone must be scrapped (scarified) and, whenever possible, equipment traffic must be minimized.

The pregnant solution contains dissolved ores; therefore, is economically imperative that no leaking whatsoever occurs through the pond. A waterproof coating is used to contain the pregnant solution and to avoid possible environmental impacts caused by its seepage (liberation).

Following metal removal in the recovery station, the barren solution contains a leaching solution. For economic and environmental reasons, the barren solution pond must likewise be contained via the waterproof coating. Before the solution is reused in a new leaching cycle, its concentration is corrected in the pond. It is common to construct both ponds adjacent to each other, confining large solution volumes in one specific area, thus minimizing construction and operation costs.

Use of ionic exchange polymeric resins in nickel selective recovery for lateritic processing is a new industrial technology. As such, it still has some constraints and operating glitches. Commercially available resins with an iminodiacetic acid group, selective for nickel and with an economically attractive cost, have two major limitations:

-   -   Given the high selectivity of H+ ions, in order for these resins         to be nickel-selective and to have high nickel adsorption         performance, pH must be increased in the solution to values         above pH=3. Otherwise, the excessive presence of H+ ions (low         pH) will preferably lead to their adsorption, thus harming         nickel adsorption.     -   Every acid leaching effluent solution of nickel ores has several         dissolved metals regarded as impurities, in addition to nickel         and cobalt. As with every resin selective to nickel, iron,         copper and aluminum, a previous stage is necessary for treatment         of the solution, eliminating such impurities.

In order to overcome both aforementioned constrains, a neutralization stage is currently used. Lime, limestone, soda or ammonia is added to simultaneously precipitate impurities and raise the pH. This procedure solves these restrictions but causes other inconveniences, such as (1) significant loss of nickel, which is precipitated with the impurities, and (2) necessity of a costly solid-liquid separations stage, following neutralization

The rich solution, concentrated in metals of interest such as nickel and cobalt, also displays impurities, which must be removed from the solution. Towards this end, there is usually a neutralization stage between leaching and resin-in-pulp (“RIP”) in order to neutralize excessive leaching effluent acid and to precipitate iron and some impurities. Temperature in this neutralization stage must be in the 70° to 95° C. range, with limestone addition and air injection, in order to oxidize iron. In this stage, pH is in the 4 to 5 range.

Several hydrometallurgical routes are being developed to extract nickel and cobalt contained in lateritic ores. These routes aim at rendering metal species soluble, using inorganic acid, through heap leaching, vats with atmospheric pressure and temperature below boiling point or pressurized vats, followed by neutralization (for Cu, Fe, Al removal) and solid-liquid separation, prior to solution purification and final recovery as metal or as intermediate product. Selective recovery of the metal present in the leaching effluent is a major stage from the economic standpoint. Presence of many impurities (copper, iron, aluminum, manganese, magnesium and others) can be regarded as the chief technological hurdle to be overcome. Using physical-chemical methods—such as ionic exchange materials, selective precipitation and extraction by solvents—could be an option. In the specific case of nickel and cobalt, these metals have very similar chemical properties, which facilitates their mutual recovery, either through precipitation as mixed sulfide products (“MSP”) or as mixed hydroxide products (“MHP”), extraction by solvents in a chloride, ammonia or sulfuric medium or, finally, through polymeric resin-type ionic exchangers.

Ionic exchange resin is regarded as an incipient technique, with no large-scale use, when compared to other options for solution treatment in nickel processing systems. Studies are being intensified and several approaches and results are so far promising. Recently, there has been considerable incentive to developing a nickel-centered technique, able to compete with conventional technologies (such as extraction by solvents and precipitation) given its operational simplicity, fewer equipment items and less cost involved. Its main upsides are an efficient recovery and removal of minor concentrations of some metallic ions with respect to: an excess of other metals, high metallic loading (charging), high mechanical resistance which reduces losses due to friction, swift elution and low losses due to contamination by organic matter. Plants that make industrial use of acid leaching for lateritic ores include a multi-stage settling circuit in countercurrent flow for solid-liquid separation. This involves high capital and operating costs, occupies large areas and demands a significant amount of washing water. Taking advantage of ionic exchange technology, one alternative to recover nickel and cobalt from leaching pulp, without using thickeners, is to use a RIP system.

RIP operation has three distinct stages. Nickel and cobalt are selectively recovered in the adsorption stage. This stage can be by air agitation or by mechanical stirring in vats. The resins suggested for this type of use are those with the iminodiacetic acid or picolylamine functional group. Resin-pulp contact is in countercurrent flow, with intermediate inter-vat screening sieves, for phase separation. The loaded (charged) resin in the first vat is withdrawn from the circuit, washed for solid aggregate removal, and transferred to the elution circuit. Elution must be carried out with chloride acid (50-150 g/L concentration) obtained in the regeneration process during pyrohydrolysis. The eluted resin then contacts a reagent—such as soda or limestone—in order to be regenerated and reverted to a calcium or sodium form.

Ionic exchange technology is being intensively developed with various promising approaches and results. The ionic exchange technique with polymeric resins, albeit still industrially unused in nickel ore flowcharts, should offer advantages such as: (1) no reagent loss by dragging, as occurs in extraction by solvent: (2) efficient recovery and removal of minor concentrations of some metallic ions in relation to an excess of other metals; (3) high selectivity for metals of interest; (4) high separation capacity; (5) flexible process regimen; (6) simple process configuration; (7) high metal of interest concentration vis-a-vis other impurities; and (8) high automation level. These features translate into lower capital and operating costs and less environmental impact (reduced water consumption and opportunities to recycle used water).

Once the metal has been extracted and rendered soluble in aqueous solution, the ionic exchange technique with resins (preferably of the chelating type) can be used in the effluent as pulp or solution, in order to recover nickel and cobalt. Use of the ionic exchange technique with polymeric resins to selectively adsorb nickel can occur in two ways:

-   -   Resin-in-Column (“RIC”): In this type of operation, a solution         with dissolved metals is percolated through a fixed resin bed         causing adsorption.     -   Resin-in-Pulp (RIP): In this type of operation, ore pulp         directly contacts the resin, through a stirring system, causing         metal adsorption with no need of previous solid-liquid         separation in the pulp, thus avoiding product loss. Following         contact, resin and pulp are separated from each other via         screening.

In nickel lateritic ore processing flowcharts, either one of these two choices may be adopted. If RIC is used, solid-liquid separation is necessary. Operating cost is high and process inefficiency leads to nickel loss because it is difficult to wash solids and recover dissolved species. This is why the other option, RIP, is preferred. Metal dissolved in the pulp is recovered after leaching with the use of an ionic exchanger. Hence, solid-liquid separation is not necessary.

It should be noted that the prior art includes several publications within the same field of technology related to the use of resin-in-pulp in the process of heap leaching effluent, but none of them teaches or suggests, the present invention

WO 01/29276A1 “Resin-in-Pulp Method For Recovery Of Nickel And Cobalt From Oxidic Ore Leach Slurry” to W. Duyvesteyn, et al. refers to a process for the recovery of nickel and cobalt from nickeliferous oxide ore leach slurry by ion exchange. It also teaches that nickel and/or cobalt are recovered by known processes. Thus, the disclosed process teaches the recovery of nickel and cobalt avoiding the use of solid/liquid separation, but without describing specifically the ways the leaching can be accomplished.

WO 96/20291 “Recovery Of Nickel And Cobalt From Laterite Ores” to W. Duyvesteyn, et al. describes a process for selectively recovering nickel by ion exchange absorption from a Ni/Co sulfuric acid feed solution obtained from limnonite ore, which is pressure leached with sulfuric acid and then neutralized and solid/liquid separated, containing nickel in the range of about 0.5 to 40 gpl and cobalt in the range of about 0.01 to 2 gpl as sulfates. The document describes that the absorbed nickel is stripped from the said resin with sulfuric acid to form a nickel sulfate solution characterized by a nickel to cobalt ratio of at least about 50:1 suitable for the recovery of substantially pure nickel by electrolysis. Thus, the document refers to the recovery of nickel merely by electrolysis, which is a well-known method for this specific technology and it also uses the solid/liquid separation.

WO 2007/087698 “Hybrid Process Using Ion Exchange Resins In The Selective Recovery Of Nickel And Cobalt From Leaching Effluents” to R. Costa (and to present inventor) is directed to a hybrid process using ion exchange resins in the selective recovery of nickel and cobalt of leaching effluents that is comprised of the steps of processing the laterite ore, which is then treated through leaching (either atmospheric or under pressure), considering solutions from the solid-liquid separation step of existing plants already in operation as well, in a way that the downstream process comprises an ion exchange hybrid circuit. Even though the document is related to the recovery of nickel and cobalt, it still mentions the solid-liquid separation without describing the heap methodology.

WO 01/32943 “Atmospheric Leach Process For The Recovery Of Nickel And Cobalt From Limonite And Saprolite Ores” to C. Arroyo, et al., deals with a hydrometallurgical process for leaching nickeliferous laterite ores at temperatures below the boiling point of the pulp and at atmospheric pressure. The high iron fraction of the laterite, referred to as limonite, is first contacted with concentrated sulfuric acid to partially or completely dissolve the iron and nickel into solution. The document states that the resulting final leach slurry can then be treated with conventional methods to recover nickel and cobalt from solution. Thus, in accordance with the document, there is no apparent novelty in relation to the recovery of such metals.

U.S. Pat. No. 4,756,887 “Process Of Heap Leaching” to S. Lesty, et al. describes a heap leaching process and comprises the following steps: (a) preparing the ground to receive the heap; (b) forming the heap; (c) sinking injection wells into the heap; (d) injecting the leaching solution by means of injection wells; and (e) recovering the leaching solution at the base of the heap, or by pumping from wells neighboring those used for injection. This patent is merely focused on the functional characteristics of a heap leaching method. Heap leaching is broadly known. It does not mention the use of such a method for the recovery of nickel and cobalt.

WO 01/75184A2 “Heap Leaching Of Nickel Containing Ore” to W. Duyvesteyn, et al. describes a method of heap leaching ore to recover nickel by forming at least one heap from a mixture of the ore and concentrated sulfuric acid; applying a leaching solution to the top of the heap at a first predetermined average flux rate wherein a leach liquor is formed at a bottom of the heap; and directing the leach liquor into a product liquor sump for direct delivery to a processing plant for substantially extracting nickel values. This document refers to the heap leaching methodology in a general sense without mentioning any kind of use of resin-in-pulp or ion exchange technology.

WO 07/87675 “Improved Base Metal Recovery Process From Heap Leaching” to M. Rodriguez, et al. discloses a process for the recovery of base metals from an oxide ore, comprising the steps of: forming at least one heap of the oxide ore containing the base metals to be recovered; irrigating at least one heap of oxide ore with a leach solution comprising sulphuric acid; collecting resulting pregnant leach solution from the irrigated heap; and treating the pregnant leach solution with a reducing gas stream to create a treated pregnant leach solution for recovery of required base metals. As a matter of fact, the process disclosed by the document is applicable to the conversion of ferric ions to ferrous ions, with regeneration of sulphuric acid in the process.

Some other publications such as U.S. Pat. No. 3,839,168 “Method For Producing High-Purity Nickel From Nickel Matte”, to L. Grandon, et al.; WO 05/045078 “A Method For The Removal Of Copper From A Zinc Sulphate Solution”, to L. Lehtiner et al.; U.S. Pat. No. 6,524,367 “Hydrometallurgical Process For The Recovery Of Nickel And Cobalt By Ammoniacal Leaching” to J. Suarez et al. and WO 2006 119559 “An Improved Process For Heap Leaching Of Nickeliferous Ores”, to H. Liu, even though dealing with nickel and/or cobalt recovery, all of them use conventional techniques of recovery and apparatus.

Thus, as can be seen from above, none of the cited representative state of the art references deal specifically with a hydro-metallurgical process using resin-in-neutralized-solution.

SUMMARY OF THE INVENTION

The present invention refers to a hydro-metallurgical process using resin-in-neutralized-solution in heap leaching effluent.

The process is applicable to lateritic ore, nickel oxidate, cobalt oxidate or a mixture containing value metals of interest—nickel, cobalt and other secondary metals—wherein ore is leached by adding an acid or a base with possible pH adjustment, aided by acid or base with neutralization of heap leaching effluent, by adding lime, limestone, soda or ammonia in the temperature of 70° to 95° C. range, at pH in the pH4 to pH5 range; wherein soluble impurity species can be reduced or cementing/complexation techniques, comprising a neutralized leaching effluent, as a slurry, made up of solid particles (precipitated compounds) and solution, but ore and ore residue-free, which is fed into the resin-in-neutralized-solution (“RINS”) circuit, with no need for solid-liquid separation; wherein the resin-in-neutralized-solution circuit comprises vats stirred in countercurrent flow and wherein the loaded resin is separated from the slurry by screening.

If RINS is used in recovering nickel from acid leaching, the following benefits are to be expected:

a) Acid leaching, followed by neutralization, can produce a hard-to-settle slurry or solids which, when separated, are difficult to wash. The RINS process can get around these operating difficulties by eliminating the solid-liquid separation stage.

b) Neutralizing solution acidity is conveniently carried out in the same adsorption stage, during contact. Inexpensive reagents, such as lime or limestone, can be used, and gypsum formed during neutralization would become part of the pulp.

c) Use of the resin, which is also iron selective, requires neutralization prior to nickel recovery. If lime or limestone is added, ferric hydroxide precipitates easily and becomes part of the neutralized solution

In any resin operation, a previous stage is needed to neutralize acidity, elevate pH, and eliminate impurities through precipitation (FIG. 2).

Following neutralization, neutralized leaching effluent, with no liquid-solid separation, goes to the stage where ion exchange with polymeric resins is directly applied to the slurry. This process is called RINS. Basically, it is an option in solution purification, with a perspective of effective and selective separation of nickel from the other impurities in the effluent. This process makes it possible to eliminate the costly solid-liquid separation and to achieve high efficiency. Major gains are thus expected in process economic savings. Furthermore, a simplification is proposed for the next stages in the present process flowchart.

A high purity product known as eluate is obtained in ion exchange. This is conducive not only to simplification of the next stages but also to simpler unit operations. The process flowchart is thus simplified; eliminating possible operational problems that are common to impure solutions. Once separated, nickel and cobalt are individually recovered. Nickel and cobalt can then be recovered as diverse products.

Below are some positive results of the invention and some of its advantages:

-   -   Increased process efficiency, high recovery rates of nickel and         cobalt.     -   Simplified process, with reduction of unit operations.     -   Minimization of operating problems usually detected in         industrial plants.     -   Less environmental impact--reduced water consumption and         opportunity for water recycling.     -   Lower operating and capital costs.     -   Enhanced quality of process final products-high selectivity of         interest metals, great separation capacity and outstanding metal         recovery efficiency.     -   Lower technical and operational risk, due to optimization of         unit operations, regarding operating conditions and reagents and         purity of PLS.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is to a schematic prior art representation of ore processing using heap leaching.

FIG. 2 is a schematic representation of the invention.

PREFERRED EMBODIMENT OF THE INVENTION

The present invention refers to a hydro-metallurgical process using resin-in-neutralized-solution of a heap leaching effluent. It provides the following advantages:

Ore leaching is preferably acid, with an option to use sulfuric or hydrochloric acid. The pregnant leaching solution (“PLS”) coming from the pile should have free acidity preferably between 02 and 200 grams per litre. One such technology is heap leaching. Downsides are less nickel recovery efficiency and higher operating cost (due to greater acid consumption). However, lower investment cost makes it a highly attractive technical alternative. Leaching yields an impurity-bearing solution and highly concentrated with metals of interest. However, neutralization is necessary to adjust this solution's pH, complying with RINS operational standards. That demands neutralizing excessive leaching effluent acid, in addition to precipitating iron and some impurities. Temperature in this stage should be in the 70° C.−95° C. range. Lime or limestone can be added and air injected in order to oxidize iron. In this stage, pH is in the 4 to 5 range. This can be done in a single step or in a two-step operation. In this case, the first stage would increase the pH to a 1.5 to 4.5 range, and the second stage to a 3.0 to 5 range.

Mention has already been made of the RINS process' advantages. Nevertheless, emphasis must be placed on the benefits of eliminating costly solid-liquid separation, of flowchart simplification as shown in FIG. 2 of the present invention, elimination of several unit operations, potential reduction of investment and operating costs, high recovery & efficiency recovery of nickel and cobalt (metals of interest).

Unless indicated to the contrary, the adverb “about” before a series of values will apply to each value in the series.

RINS operation occurs in stirred vessels. Stirring can be mechanical or by air agitation. A pachuca vessel is preferred. It's bottom is cone-shaped and from a center draft tube air is injected into the tank containing a solid-liquid mixture. The pachuca air-stirring system has the advantages of reduced physical degradation of the resin and better RINS particle dispersion when compared to mechanical stirring. The slurry cascades down by gravity, from vessel to vessel, displaying approximately 25% to 45% of solids, preferably 35%. Resin-in-Neutralized-Solution operation must take place at an adequate temperature, coherent with the resin's thermal stability limit (about 80° C.). Generally, the adsorption rate will increase as the temperature rises, due to better slurry viscosity.

Slurry residence time can be up to twelve hours (30 to 60 minutes per stage) and it is influenced by the size of the feeding material particles. Resin volume in each stage is roughly 10% to 30% of slurry volume in the vessel. The resin advances in countercurrent flow, from one stage to another, through pumping or pneumatically hauling both slurry and resin to the next adsorption stage. The loaded (charged) resin leaves the first adsorption stage and is pumped to a static or vibrating horizontal screen, to be washed and separated from the pulp. Preferably, the resin is composed of the bis-picolylamine or iminodiacetic acid functional group.

Once the resin has been loaded (charged) with metals, it is physically separated from the slurry. Screening separates larger-diameter resins from the slurrys fine particulates. Exiting the first adsorption stage, the resin is sieved for separation and washing. Washed, humid and drained, the resin next goes to the elution circuit, for nickel and cobalt desorption Elution can be initially with acidified water (preferably pH 2), to remove iron adsorbed in the resin. Next is the use of ammonium salt (ammonia sulfate or hydroxide) for copper removal. Finally, acid is used (0.50 to 4M, preferably 1M) for nickel and cobalt elution. After elution and, if necessary, the resin can be regenerated and ions (such as Na+, Ca2+) can be included as mobile ions. The eluate obtained in this stage may contain nickel concentrations above 45 g/L with low impurity concentrations. This high-purity product must be sent to a unit operation, for the sole purpose of Ni and Co separation (through extraction by solvents or continuous ion exchange). Following their separation, nickel and cobalt may be separately recovered in various ways.

In the present process, the ore and ore residue-free slurry obtained in neutralization is fed to the RINS unit. Following neutralization, the leaching effluent is ore and ore residue-free and preferably contains solid compounds of precipitated aluminum and iron. Thus, the present invention provides the use of a RINS (resin-in-neutralized-solution) system as an alternative to recover nickel and cobalt from heap leaching effluents, with no solid-liquid separators, such as thickeners. This type of ionic exchange process directly applied to the slurry eliminates costly solid-liquid separation and offers greater efficiency in recovering nickel contained in the leaching effluent, in view of the desorption-leaching phenomenon, which recovers nickel in both the solid and liquid phases.

While in accordance with the provisions of the statute, there is illustrated and described herein specific embodiments of the invention. Those skilled in the art will understand that changes may be made in the form of the invention covered by the claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features. 

1. A hydrometallurgical process for recovering value applicable to an initial material selected from the group consisting of lateritic ore, nickel oxidate, cobalt oxidate or a mixture containing metals of the group consisting of nickel, cobalt and other secondary metals using a resin-in-neutralized-solution in a heap leaching effluent, the process comprising: a) leaching the initial material by adding an acid or a base, b) adjusting the pH of the initial material with an acid or base, simultaneously with optimized and selective loading of nickel and cobalt in multiple ionic-exchange stages, c) neutralizing the heap leaching effluent by adding a neutralizing agent selected from the group consisting of magnesia, lime, limestone, soda and ammonia at a neutralizing temperature between about 70° and 95° C.; and injecting air thereto at a pH in the range of about 4-5, d) reducing a soluble impurity species in the heap leaching effluent, e) feeding the resultant neutralization product into the resin-in-neutralized-solution circuit with no need for solid-liquid separation, f) separating the loaded resin from the resin neutralization solution slurry, in which the slurry's residence time is influenced by the size of the initial material's particles, the resin volume in each multiple ionic-exchange stage is about 10% to 30% of the slurry volume in each vat holding each stage, and g) wherein the loaded resin exits a first adsorption stage and is pumped to a screen.
 2. The process according to claim 1 wherein the leaching effluent is neutralized as slurry and is made up of solid particles and solution but ore-free.
 3. The process according to claim 1 wherein the resin-in-neutralized-solution circuit includes the vats stirred in countercurrent flow.
 4. The process according to claim 1 wherein the secondary metals are selected from the group consisting of copper, iron, chromium, aluminum, magnesium, manganese and calcium.
 5. The process of claim 1 wherein an acid acting as leaching agent is selected from the group consisting of sulfuric, chloride or nitric type.
 6. The process according to claim 1 operating including under atmospheric pressure conditions and temperature below about 80° C.
 7. The process according to claim 1 wherein the leaching effluent's pH is adjusted by an acid or base according to selected from the group consisting of hydroxides, oxides and carbonates.
 8. The process according to claim 1 wherein impurities such as trivalent iron and copper are eliminated from the solution through cementing/complexation techniques by adding an agent from the group consisting of iron, aluminum or metallic magnesium.
 9. The process according to claim 1 wherein reducing agents are added in order to reduce impurities.
 10. The process according to claim 1, wherein impurities are precipitated by adding sulfides selected from the group consisting of H₂S, NaHS, Na₂S.
 11. The process according to claim 1 wherein hexavalent chromium is eliminated from the resin-in-neutralized solution by adding a reducing agent.
 12. The process according to claim 1 wherein the heap leaching effluent, following neutralization and having undergone pre-treatment to eliminate impurities, is directly fed to the resin-in-leach neutralized solution stage with no need for solid-liquid separation.
 13. The process according to claim 1 wherein the resin-in-neutralized-solution stage includes stirred vats.
 14. The process according to claim 1 wherein the resin neutralized solution slurry cascades down by gravity from vat to vat, containing about 25% to 45% of solids.
 15. The process according to claim 1 wherein the resin-in-neutralized-solution separation occurs at an adequate temperature, coherent with the resin's thermal stability limit.
 16. The process according to claim 1 wherein the resin neutralized solution slurry's total residence time is up to about twelve hours and at about thirty to sixty minutes per stage.
 17. The process according to claim 1 wherein the resin volume in each stage is about 10% to 30% of the pulp volume in the vat.
 18. The process according to claim 1 wherein the resin advances from stage to stage in countercurrent flow.
 19. The process according to claim 1 wherein the loaded resin exits a first adsorption stage and is pumped to a screen.
 20. The process according to claim 1 wherein the resin is selected from the group consisting of the functional groups of type 2 picolylamine, bis(2 picolyl)AMINE, n-METIL-2PICOLYLAMINE, n(2HYDROXIETIL)2PICOLYLAMINE, n(2HIDROXIPROPIL)2PICOLYLAMINE.
 21. The process according to claim 1 wherein metal elution can occur selectively and in the multiple stages.
 22. The process according to claim 1 wherein elution with acidified water (pH 2) removes iron adsorbed in resin.
 23. The process according to claim 1 wherein an ammonium salt is used for copper removal.
 24. The process according to claim 5 wherein the concentration of the acid is between about 0.5 and 4M for nickel and cobalt elution.
 25. The process according to claim 24 wherein the concentration is about 1M.
 26. The process according to claim 1 wherein the resin is regenerated and ions such as Na+, Ca2+ can be included as mobile ions.
 27. The process according to claim 1 wherein nickel and cobalt in high concentrations in the eluate and with no impurity interference are separated from each other by extraction methods selected from the group selected from solvents and ionic exchange.
 28. The process according to claim 1 wherein nickel is sent to an electrolysis unit for recovery in a predetermined form.
 29. The process according to claim 1 wherein cobalt is recovered as an intermediary product selected from the group consisting of sulfides, hydroxides and carbonates. 